1. Field of the Invention
The present invention relates to a vehicle suspension mechanism, more particularly to a suspension mechanism provided with a swing arm extending in a longitudinal direction of a vehicle body with the swing arm being connected with the vehicle body.
2. Description of the Prior Art
There has been proposed a vehicle suspension mechanism provided with a swing arm extending longitudinally and a plurality of lateral links extending transversely for carrying vehicle wheels. For instance, Japanese Patent Public disclosure No. 60-53408 discloses a suspension mechanism provided with a swing arm extending longitudinally and swingably connected at the front end portion thereof with a shaft mounted on a vehicle body.
With this structure, the swing arm is subjected to a force which causes the swing arm to displace vertically and horizontally about a joint portion thereof with the vehicle body in bumping and rebounding action of the vehicle. Thus, a resilient property of the joint portion of the swing arm affects a suspension property.
In order to provide the joint portion with a desirable property and an improved durability to thereby obtain a desirable suspension mechanism, Japanese Patent Public Disclosure Nos. 62 55206, laid open to the public on Mar. 10, 1987, and 62-134308, laid open to the public on June 17, 1987 disclose suspension mechanisms in which a joint structure between a swing arm and a vehicle body is provided with a holder member rotatably connected with the vehicle body through a longitudinally extended shaft about which the holder member is rotated and an arm member carried by the holder member for swingably carrying a swing arm in an up and down direction about a shaft mounted on the arm member and allowing the swing arm to displace slightly in the longitudinal direction of the vehicle.
In the joint structures between the vehicle body and the swing arm of the suspension mechanism as disclosed in the prior art aforementioned, there is provided a rubber bushing so as to absorb a vibration transmitted from the vehicle wheels and a torsional force acting on the joint structures.
In this regard, it is necessary for the rubber bushing to have a soft resilient property for accomplishing an improved riding comfort. It should however be noted that a soft property of the rubber bushing is apt to produce a vibration of the vehicle body when a speed change is produced in the vehicle, specifically in an abrupt starting action. This is because such soft rubber bushing allows a delayed movement of the vehicle body relative to the vehicle wheels.
This means that it is difficult to provide a suspension mechanism with a desirable property by merely disposing a rubber bushing at the joint portion between the vehicle body and the swing arm.
Under these circumstances, there is proposed a joint structure having a rubber bushing formed with oil chambers filled with an oil. However, this proposed structure is disadvantageous in that the oil chambers of the rubber bushing are deformed when they are subjected to a torsional force so that a desirable effect cannot be obtained.